HIF1A and neoplasm: To address the role of HIF‐1 in the regulation of the BCSC phenotype, we transfected MDA‐MB‐231 with a HIF‐1 expression fluorescent tracking system[36] (Figure 3D), implanted the cells into SCID mice, treated mice with paclitaxel, collected tumor tissues after treatment, and sorted cells into DsRed+/GFP− (HIF‐1−) or GFP+ (HIF‐1+) populations (Figure 3E).